This invention relates to a scanner operative in an imaging system for moving a subject past an optical beam to accomplish an optical scanning of the subject and, more particularly, to the use of a drum and a pair of rollers for guiding the subject along a path of travel past a viewing site at the light beam, and wherein a spacing between the rollers can be varied in synchronism with rotation of the drum to facilitate transfer of a leading edge of the subject between rollers prior to presentation of the subject to the light beam for the optical scanning.
Scanners providing for optical scanning of a subject are constructed frequently with mechanical components which move a subject along a path of travel past a viewing site where the subject is scanned by an optical beam. One form of apparatus for accomplishing the movement of the subject includes a drum having a cylindrical surface disposed at the viewing site, and includes two rollers disposed in contact with the drum and located at opposite sides of the viewing site. Rotation of the drum brings successive portions of the subject into the viewing site while pressure between the rollers and the drum secures the subject to the drum to enable accurate positioning of the successive portions of the subject during the scanning procedure.
It may be desirable to construct the scanning apparatus in a manner which admits the subject into the scanner by rotation of the drum in a forward direction for the purpose of ascertaining the physical size of the subject, this being followed by retraction of the subject by rotation of the drum in the reverse direction. The scanning of the subject by the optical beam takes place during the retraction of the subject. Such a scanning procedure is useful because an image processor operative in conjunction with the movement of the subject can be provided with information as to the physical size of the subject prior to the actual optical scanning.
A problem arises in the use of such a scanner in that the spacing between the rollers requires that the subject have a physical form which facilitates advancement of the subject from a first nip between a first of the rollers and the drum to a second nip between the second of the rollers and the drum. Typically, the subject is in the form of a photograph or a picture postcard, such card-shaped subject having a leading edge, a trailing edge, and opposed side edges. The card may be inserted manually into the first nip such that, upon rotation of the drum, the card is drawn past the viewing site to be engaged in the second nip. However, should the leading edge portion of the card be bent or otherwise disfigured by handling by persons viewing the card, or by other causes, there is a chance that the leading edge, during advancement of the subject, may deflect away from the second nip and pass over the second roller rather than through the nip. This would disrupt the scanning procedure.